Potion Cauldron STEM / STEAM Activity

Background

For the Halloween event at my local Children's Discovery Museum, we wanted to do something in the the science room.  We decided to do a potion mixing activity (baking soda + vinegar + food coloring + dish soap).  To make it more fun, and contain the mess I put this model together.  The inner bowl contains the reaction, and it spills over into the cauldron. I only had a couple days to design and print up 4 for the event.  So I started with the "Cauldron for Whirling Witchcraft" by mnemic and adapted it for our purpose.  If you want a simple cauldron that scales well and does not need supports, I highly recommend it.

Printing notes

No supports needed. Your standard print settings should work fine.
I used a 0.6mm nozzle, 3 walls, 10% infill.  I used some old rolls of PLA, nothing fancy.
All parts are oriented as I printed them.  If you struggle with bed adhesion, you may want to rotate the inner bowl 180% so the wide end is on the print bed. 

How we ran the activity

Activity Prep
The vinegar solution:
We used 4 cups vinegar + 2 cup water + 1/4 cup dish soap.  The water and dish soap creates a reaction that is slower and creates lots of bubbles that last for 10-20 minutes.  You can play with the ratios but this is what worked for us.

1. Fill 10ml vials with 5-6ml (1 tsp) baking soda. 

2. Fill 20ml vials with 15-18ml (3 tsp) vinegar solution.

3. Add 1-2 drops of food coloring to the vinegar solution vials. The younger kids really enjoyed it when I added the color while they were at the station.  I would add the color, cap the vial, then turn the vial upside down to mix them. The kids would ooh and ah as the color filled the vial.

Activity Part 1: Potion Mixing

1. The kids were given one small vial with baking soda and instructed to empty it into the inner bowl. 

2. They then choose two colored vials and poured them into the inner bowl.  They could pour them in at the same time, one at a time, or alternated between them.  Each method of adding the colored vials results in a different colored reaction, varying swirls of color to one solid color.

Activity Part 2: Potion Painting

1. Once the reaction completes the kids were given a piece of paper and a pipette to make pictures with their potion. 

2. They could use the pipette as a paint brush or use it to drop blobs of color. The potion mixture goes on dark but becomes more of a watercolor tie-dye once it dries. 

3. When the kids were done with their art, the pages were placed on a paper towel and set aside to dry.  Most of the pages dried in an hour or two. 

Activity Cleanup
To reset between runs we just emptied the inner bowl and cauldron then gave them a quick rinse in the sink. We then dried the outside of the cauldron and they were ready for the next run. The vials were all refilled as needed, no need to rinse between runs. 

Overall this activity was a big hit. A few of the parents even made their own potions and art. This will become a regular activity at the museum.